Logging to a different local facility?

Hmmm, the local5 facility is used for local logging of packet filter messages. However, I'm sure you could do something smart with syslog-ng, which is what is used by TMOS. Some customer destinations and filters and the like should do the trick.

You can find manuals here: http://www.balabit.com/support/documentation.

Be aware that the F5 configuration will be slightly different and you need to be careful that your changes are not overwritten. This will help you in some way I'm sure: https://support.f5.com/kb/en-us/solutions/public/13000/300/sol13333.html.

Either way, this is going to be quite a job!